Chip-card with mode switching between contactless and contact-coupled mode

ABSTRACT

A chip card is operable in a contactless and contact-coupled mode. For operation in the contactless mode, the chip card has an antenna coil and rectifier. In the contactless mode, the chip card receives an AC signal. The rectifier provides a rectified received AC signal. The rectified signal is used for powering internal circuitry of the chip card. The chip card further has a recognition circuit that recognizes whether an AC signal is actually received by the antenna coil. If the AC signal is recognized, the recognition circuit switches the chip card to the contactless mode. If no AC signal is recognized, the recognition circuit switches the chip card to the contact-coupled mode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chip-card which can be coupled to anassociated write-read station via contacts as well as via at least oneantenna coil, the write-read station supplying the operating power forthe chip-card via the coupling and the data exchange also taking placevia this coupling, a rectifier being provided to supply power in thecase of coupling via the antenna coil(s).

2. Description of the Related Art

A chip-card of this kind is known from DE-C-39 35 364. Chip-cards arehighly integrated electronic units (chips) packed in a syntheticmaterial with the format of a credit card. Depending on the relevantfield of application, there are nowadays, for example electronic traveltickets, GSH cards, telephone cards and many others. In conformity withthe field of application, the electronic units deviate from one anothernotably in respect of parameters such as storage capacity, accessprotection, data transmission rate, flexibility and transmissiondistance for contactless chip-cards.

Most chip-cards have a contact bank for the contact-coupled mode ofoperation. Lately, however, increasing numbers of contactless cards areused which feature notably a higher reliability, easier handling andbetter protection against vandalism for the associated contactlesswrite-read stations. In the contactless mode, the transfer of power andclock signals to the electronic circuitry of the card, or thebidirectional data transmission, is realized via inductive couplingbetween the antenna of the write-read station and the antenna coil ofthe chip-card. The supply voltage for the chip-card is formed byrectification of an RP signal transmitted by the write-read station. Inthe contact-coupled mode of operation, the supply voltage, clock signalsand data are conducted via separate contacts.

DE-C-39 35 364 already discloses a chip-card which can operate viacontacts as well as via inductive coupling. The modes of operation canbe activated at option and with full equality by using either acontactless or a contact-coupled write-read station.

According to DE-C-39 35 364 for this purpose there is provided amultiplexer which receives on the one hand the signals from the contactsof a contact bank and on the other hand the appropriately preparedsignals from the coils (supply voltage, clock signals, data). A circuitof the type also provided in chip-cards constructed exclusively foroperation in the contact-coupled mode is connected to the outputs of themultiplexer (for example, an arithmetic circuit and a storage unit). Inorder to define which signals are switched to the outputs by themultiplexer (the signals present on the contacts of the contact bank orthe appropriately prepared signals received from the coils), there isprovided a comparator which compares the DC voltage derived from the RFsignal received from the coils with the DC voltage present on thecontact bank.

It is a drawback of this circuit that the operating voltage is alsoconducted via the multiplexer in which inevitably a given voltage dropoccurs. Therefore, the operation of this circuit will be poor in thefringe range (in the case of a large distance between the write-readstation and the chip-card).

SUMMARY OF THE INVENTION

It is an object of the presert invention to provide a chip-card of thekind set forth in which the range in the contactless mode is equal to oronly insignificantly shorter than in chip-cards which are suitableexclusively for contactless operation.

According to the invention, this object is achieved by means of achip-card of the kind set forth in that the rectifier is connecteddirectly to components requiring operating voltage, and that there isprovided an AC recognition circuit for switching the chip-card betweenthe two modes of operation “coupling via the contacts” and “coupling viathe antenna coil(s)”.

Thus, the voltage generated in the rectifier is applied directly to thecomponents requiring operating voltage, so that this full voltage isavailable as in the case of chip-cards which are suitable exclusivelyfor the contactless mode of operation. Therefore, ignoring a slightlyhigher power consumption, the range is approximately the same as inchip-cards constructed exclusively for the contactless mode.

Due to this step, however, a mode-switching circuit of the kind providedin DE-C-39 35 364 is not possible; because the rectifier is connecteddirectly to the components requiring operating voltage, it alwayscarries a voltage, irrespective of whether it is supplied by therectifier itself or by a contact of the contact bank. (This is not thecase in the circuit known from DE-C-39 35 364, because the supplyvoltage is applied to the components requiring operating voltage via themultiplexer.) Therefore, according to the invention there is provided anAC recognition circuit (for example, in the form of an additionalrectifier) for switching between the modes of operation. If this circuitrecognizes an AC voltage on the antenna coil, the chip-card is switchedto the contactless mode of operation (“coupling via the antennacoil(s)”) and otherwise to the contactcoupled mode of operation(“coupling via the contacts”).

As an alternative for the AC recognition circuit the contact supplyingthe supply voltage may be decoupled from the rectifier, for example bymeans of a diode, and a voltage recognition circuit may be connected tothis contact in order to switch the chip-card between the two modes ofoperation “coupling via the contacts” and “coupling via the antennacoil(s)”. When this circuit detects a voltage on the contact, thechip-card is switched to the contact-coupled mode of operation(“coupling via the contacts”) and otherwise to the contactless mode ofoperation (“coupling via the antenna coil (s)”).

Thus, in the first case the mode of operation is governed by whether ornot an AC voltaga is induced into the antenna coil whereas in the lattercase it is governed by whether or not a DC voltage is present on therelevant contact. A combination of the two possibilities is alsofeasible.

Preferably, not more than one antenna coil is provided. A chip-cardwhich is designed exclusively for contactless operation and does notrequire more than one antenna coil is described in AT-B-395 224. If thetransmission system disclosed therein is used in the context of thepresent invention, the circuit will feature the minimum number ofelectronic components, being only one coil, one chip and one contactbank, and will also have interface switching which can be simplyimplemented from an integration point of view.

Preferably, the memory access authorizations can be configureddifferently in dependence on the modes of operation “coupling via thecontacts” and “coupling via the antenna coil(s)”. There may notably beprovided two memory sections which are alternatively activated independence on the modes of operation “coupling via the contacts” and“coupling via the antenna coil(s)”. Thus, one and the same card canperform two completely different functions in dependence on the mode ofoperation in which it is used (for example, electronic travel ticket inthe contactless mode and telephone card in the contact-coupled mode).

In the mode “coupling via the antenna coil(s)” the circuit componentswhich are not required in this mode are very advantageously controlledto a power-saving rest state in order to achieve a maximum transmissionrange. The range then equals that of a chip-card designed exclusivelyfor the contactless mode.

When the chip is mounted on the underside of the contact bank and isconnected, via two terminals, to a wound, etched or printed antenna coilembedded in the chip-card, a very large antenna coil can be used; thisis beneficial for the range. A chip-card can be particularly simplymanufactured, however, if the antenna coil is integrated with the chip.In that case it is again effective to mount the chip with integratedantenna underneath the contact bank. A compromise between simplicity ofmanufacture and size of the antenna coil consists in that the chip ismounted on the underside of the contact bank and is connected, via twoterminals, to a small antenna winding which, like the chip, is alsosituated, underneath the contact bank in the contact module.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be described in detail hereinafter with reference tothe accompanying drawings. Therein:

FIG. 1 is a diagrammatic representation of the electric circuit with aminimum number of individual components;

FIG. 2 shows a feasible encapsulation of this circuit in a plastic card;

FIG. 3 shows the electric block diagram of the monolithicallyintegratable circuit (chip); and

FIG. 4 shows a block diagram which is similar to that of FIG. 3 butrelates to another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

As appears from FIG. 1, a monolithically integrated circuit or chip 2includes terminals LA, LB for an antenna coil 3 and terminals VDD, VSS,DOUT, DIN, CLK, RESET for a contact bank 1. (The supply voltage ispresent between VDD and VSS; data is transmitted to the write-readstation via DOUT; data is transmitted to the chip-card via DIN; a clocksignal is transmitted to the chip-card via CLK; a reset signal isapplied thereto via RESET.) As is shown in FIG. 2, the chip 2 is mountedon the underside of the contact bank 1 as is customary in cards designedexclusively for the contact-coupled mode. An antenna coil 3, consistingof a few turns, is embedded in the chip-card 4 and is wound, etched orprinted as desired. Therefore, pure contact-coupled card technology canbe simply expanded to contactless operation, if an appropriate chip isused, by additionally connecting the chip 2, provided underneath thecontact bank 1, via two terminals, to an antenna coil 3 embedded in thechip-card 4. The chip 2 comprises components requiring supply voltage,and circuit components not required in contactless mode of operation ofthe chip-card. A further antenna coil may be coupled to the chip.

For a given card format the embodiment shown in FIG. 2 offers a maximumrange in the contactless Lode because the antenna coil 3 is now placedso that the winding surface area is maximum.

However, other antenna arrangements are also feasible in the context ofthe present invention so that, for example one and the same card cansatisfy the international standards for contact-coupled cards (ISO 7816)as well as for contactless cards (ISO 10536). Furthermore, thepossibility of combination with magnetic strips is completelymaintained.

The function of the chip 2 will now be described with reference to FIG.3. In the contactless mode power, clock signals and data are receivedand data is transmitted via LA and LB. A transmission method which issuitable for this purpose is disclosed in AT-B-395 224. The RF signalreceived is rectified in a rectifier 5, smoothed by a capacitor 7 andlimited by a parallel regulator 6 (being a zener diode in the simplestcase). The clock signals for the chip circuit are derived from the ACvoltage in a clock signal preparation circuit 8. The data received isprepared in a demodulation stage 9 and a modulation stage 10 returnsdata. A level recognition circuit 11 indicates the surpassing of theminimum operating voltage required. In order to implement contactlessand contact-coupled interfaces on the same chip 2, automatic recognitionof the mode of operation is required for activation of the correctinterface. This is realized by means of an AC recognition circuit 12which activates the contactless interface if an AC voltage is present onthe antenna coil 3 and otherwise the contact-coupled interface. Acontrol unit 13 controls either the contactless or the contact-coupledinterface in dependence on the mode of operation, and controls theaccess to a data memory 14 via a unidirectional address bus and abidirectional data bus. The data memory 14 comprises a first and asecond memory section.

The control unit 13 consists of four sections: section 13 a comprisesthe circuits which recognize whether the chip-card is in operation (thisis determined by the level recognition circuit 11) and, if so, whichinterface is active. Section 13 b comprises the circuits which activatethe contactless interface, and section 13 c comprises the circuits whichactivate the contact-coupled interface. Finally, section 13 d comprisesthe circuits required for both modes of operation (therein, for examplethe data are fetched from the data memory 14). In order to minimize thepower consumption (important notably in the contactless mode in order toachieve a large range), either the section 13 b or the section 13 c isset to a power-saving rest state in dependence on the mode of operation.

The control unit 13 can be implemented in a variety of ways inconformity with the relevant application:

a wide variety of protocols and baud rates for contactless and/orcontact-coupled interfaces

cryptography, authentification, PIN

memory access protection with separate memory access sections, viacontactless or contact-coupled interface in dependence on the mode ofoperation,

implementation by means of microprocessor or logic gates,

reduction of power consumption by de-activation of components which arenot required in the contactless mode of operation,

anti-collision procedure for contactless mode of operation of aplurality of cards at the operating distance from a write-read stationetc.

In conformity with the foregoing description a chip-card can be realizedwith a minimum number of individual components and hence with a minimumwork effort; such a chip-card can be operated via a contactlessinterface as well as via a contact-coupled interface, without loss offunctionality or compatibility with the standards.

FIG. 4 deviates from FIG. 3 in that the AC recognition circuit 12 isabsent. Instead a diode 15 is connected between the terminal VSS and therectifier 5, which diode decouples the terminal VSS from the rectifier5. Therefore, the terminal VSS does not carry a voltage if the operatingvoltage is supplied by the antenna coil 3; a voltage is present thereononly if the operating voltage is supplied by the contact connected tothe terminal VSS. The terminal VSS is connected directly to the controlunit 13 so that the latter can recognize the mode of operation by meansof a voltage recognition circuit.

What is claimed is:
 1. A chip-card comprising: components requiring asupply voltage; a rectifier; an antenna coil coupled to the rectifier; acontact; a control unit; and an AC recognition circuit for recognizingan AC-signal received by the antenna coil and for converting therecognized the received AC-signal to a DC control signal, the ACrecognition circuit not being comprised in the components, the chip-cardbeing operable in a contact-coupled mode of operation via the contactand a contactless mode of operation via the antenna coil, a write-readstation supplying the supply voltage to the chip-card when coupled tothe chip-card, in order to avoid voltage losses both the rectifier andthe contact being directly connected to the components, and the DCcontrol signal being provided to the control unit that controls thechip-card to switch between the contact-coupled and contactless modes ofoperation.
 2. A chip-card comprising: a memory; a controller coupled tothe memory; an antenna coil via which the chip card operates in acontactless operating mode; a contact used via which the chip-cardoperates in a contact-coupled operating mode; and switching means forswitching the chip-card in the respective contact-coupled andcontactless modes; a write-read station supplying a supply voltage tothe chip-card when coupled to the chip-card, and the controller beingconfigured to control a first memory access authorization to the memorywhen the chip-card is in the contact-coupled mode, and a second memoryaccess authorization to the memory when the chip card is in thecontactless mode of operation.
 3. A chip-card as claimed in claim 2,wherein the memory comprises a first memory section that is accessed inthe contact-coupled mode and a second memory section that is accessed inthe contactless mode.
 4. A chip-card as claimed in claim 3, wherein thefirst and second memory sections are programmed to perform a first and asecond function, respectively.
 5. A chip-card comprising: componentsrequiring a supply voltage; a rectifier; an antenna coil coupled to therectifier; a contact; a controller, a memory coupled to the controller,and an AC recognition circuit for recognizing an AC-signal received bythe antenna coil, the chip-card being operable in a contact-coupled modeof operation via the contact and a contactless mode of operation via theantenna coil, a write-read station supplying the supply voltage to thechip-card when coupled to the chip-card, both the rectifier and thecontact being directly connected to the components, the AC recognitioncircuit being configured to cause the chip-card to switch between thecontact-coupled and contactless modes of operation, and the controllerbeing configured to control a first memory access authorization to thememory when the chip card is in the contact-coupled mode, and a secondmemory access authorization to the memory when the chip card is in thecontactless mode of operation.
 6. A chip-card as claimed in claim 5,wherein the chip card comprises at least a further antenna coil.
 7. Achip-card as claimed in claim 5, wherein the components, the rectifier,the AC-recognition circuit are comprised in a chip, the chip beingmounted on beneath a contact bank that comprises the contact, and beingconnected, via terminals of the chip, the antenna coil being embedded inthe chip-card.
 8. A chip-card as claimed in claim 5, wherein thecomponents, the rectifier, the AC-recognition circuit are comprised in achip, and the antenna coil is integrated on the chip.
 9. A chip-card asclaimed in claim 8, the chip is mounted underneath a contact bank thatcomprises the contact.
 10. A chip-card as claimed in claim 5, whereinthe components, the rectifier, the AC-recognition circuit are comprisedin a chip, and the antenna coil is comprised of an antenna winding thathas a dimension that is small as compared to a dimension of the chipcard, the antenna winding and the chip being mounted underneath acontact bank that comprises the contact.
 11. A chip-card as claimed inclaim 5, wherein the memory comprises a first memory section that isaccessed in the contact-coupled mode and a second memory section that isaccessed in the contactless mode.
 12. A chip-card as claimed in claim11, wherein the first and second memory sections are programmed toperform a first and a second function, respectively.